It is well known that lead gasoline additives have been under attack due to environmental reasons. As a result, there has been a search for suitable octane improvers that do not employ lead. Various manganese compounds have been found and are known to improve the octane rating of gasoline compositions, see for example U.S. Pat. No. 3,127,351.
Discovery of these new manganese additives has presented additional problems in that now compatible additives must be found which alleviate problems caused by the use of manganese.
One problem encountered with the use of manganese additives is spark plug gap bridging and the resultant misfiring and engine malfunction. These misfires appear to be caused by formation during combustion of manganese containing particles which become lodged in the spark plug gap. For automobiles equipped with catalytic converters, such misfires overload the catalytic muffler with hydrocarbons to be oxidized and cause overheating of the converter. Also, the particles formed upon combustion of manganese containing fuels can cause clogging of the catalytic mufflers.